1. Field of the Invention
The present invention relates to a developing process and a developing unit for supplying developing solution to the front surface of a substrate such as a semiconductor wafer or an LCD substrate.
2. Description of the Related Art
In a resist process of a semiconductor fabrication, resist solution is coated as a resist film on the front surface of a substrate such as a semiconductor wafer (referred to as wafer). A predetermined pattern is formed on the front surface of the wafer by an exposing unit. Developing solution is coated to the front surface of the wafer. Thereafter, a rinsing process for rinsing the developing solution with pure water is performed.
Developing solution is supplied as a liquid layer to the front surface of the wafer. In this state, the developing process is performed for a predetermined time period. In the developing process, a positive photoresist of which an exposed portion is dissolved with developing solution has been widely used because a high resolution can be obtained.
In the developing process, a developing solution supplying nozzle portion having a plurality of spray openings arranged along a straight line is used. While the wafer is rotated at low speed, the developing solution is sprayed from the developing solution supplying nozzle portion to the front surface of the wafer. Thus, the developing solution is equally supplied from the developing solution supplying nozzle portion to the front surface of the wafer. In the rinsing process, while the wafer is rotated at high speed, pure water is supplied from a pure water supplying nozzle portion to the front surface of the wafer.
As the integration of devices are becoming high, photolithography technologies corresponding to fine design rules are desired. In this case, technologies for accurately exposing and developing a fine circuit pattern against a resist film are required. Thus, a short wavelength light source required for the exposing process should be used. In addition, the concentration and temperature of developing solution used for the developing process should be accurately controlled. In particular, with respect to the concentration of the developing solution, when the developing solution is coated as a liquid layer on the front surface of the wafer, the concentration of the developing solution should be equal on the entire front surface. In this case, since the line width of a fine circuit pattern can be suppressed from fluctuating, an equal line width can be developed.
However, in the conventional developing process, as shown in FIG. 18, when developing solution is coated as a liquid layer and an exposed portion of a resist film 101 is dissolved with the developing solution 100, a resist component dissolves in the developing solution and thereby the equality of the concentration of the developing solution deteriorates. When developing solution 102 reacts with the resist film 101, the reaction speed of the developing solution 102 becomes higher than that of the pure developing solution 100. Thus, as shown in FIG. 18, the developing speed of the resist film 101 coated with the developing solution 102 as a liquid layer reacted with the resist film 101 is different from the developing speed of the resist film 101 coated with the pure developing solution 100 as a liquid layer. Thus, as the developing process advances, the equality of the concentration of the developing solution deteriorates. Consequently, since the front surface of the wafer is unequally developed, the line width of the circuit pattern may deviate to some extent. In addition, as described above, since a high resolution circuit pattern has been required, a slight deviation of the line width may cause the yield to deteriorate. Technologies that effectively solve such a problem have not been proposed.
In addition, when a rinsing process is performed for a wafer that has been developed, if pure water is directly supplied to the front surface of the wafer, a resist component that has not dissolved in the developing solution on the front surface of the wafer solidifies. The solidified component adheres to the front surface of the wafer and thereby particles take place.
In addition, as the productivity improves, the throughput of the developing unit should be also improved. However, in the conventional developing unit, a developing solution supplying nozzle portion and a rinse solution supplying nozzle portion should be separately operated. These supplying nozzle portions should be switched corresponding to the developing process and the rinsing process. Thus, it takes a time to switch the operation of the developing solution supplying nozzle portion to the operation of the rinse solution supplying nozzle portion. Consequently, with the conventional developing unit, the throughput cannot be improved. In addition, to operate the developing solution supplying nozzle portion and the rise solution supplying nozzle portion, at least two driving means are required. Thus, the structure of the entire unit is complicated and the size thereof becomes large.
Therefore, an object of the present invention is to provide a developing method and a developing unit that allow the equality of the concentration of developing solution to be maintained.
Another object of the present invention is to provide a developing method and a developing unit that allow a developing process to be smoothly advanced to a rinsing process.
A further object of the present invention is to provide a developing method and a developing unit that allow a process time to be shortened and the structure of the unit to be simplified.
A first aspect of the present invention is a method for performing a developing process for the front surface of a substrate, comprising the steps of (a) supplying a mixture of developing solution and pure water to the front surface of the substrate, and (b) supplying developing solution to the front surface of the substrate, wherein the step (b) is preceded by the step (a).
According to the first aspect of the present invention, when the developing process is performed, after pure water is supplied to the front surface of a substrate, while the mixing ratio of a mixture of developing solution and pure water is gradually increased, the mixture is supplied. Thus, processing solution supplied to the front surface of the substrate is substituted from pure water to developing solution. Consequently, a developing component gradually reacts with a resist component. Even if the resist component dissolves in the mixture of the developing solution and the pure water, the equality of the concentration of the developing solution can be properly maintained. As a result, the developing process can be suppressed from being unequally performed.
A second aspect of the present invention is a method for performing a developing process for the front surface of a substrate, comprising the steps of (a) supplying developing solution to the front surface of the substrate, and (b) supplying a mixture of developing solution and pure water to the front surface of the substrate.
According to the second aspect of the present invention, when the rinsing process is performed, while the mixing ratio of a mixture of developing solution and pure water is gradually decreased, the mixture is supplied to the front surface of the substrate. Thus, the processing solution supplied to the front surface of the substrate is substituted from the developing solution to the pure water. Thus, the substitution from the developing solution to the pure water can be gradually performed. Consequently, particles due to the solidification of unsolved resist can be prevented.
A third aspect of the present invention is a unit for supplying developing solution to the front surface of a substrate, comprising a first supplying path for supplying the developing solution, a second supplying path for supplying pure water, a mixing portion, connected to the first supplying path and the second supplying path, for mixing the developing solution supplied from the first supplying path and the pure water supplied from the second supplying path, and a spraying portion for spraying solution mixed by the mixing portion to the substrate.
According to the third aspect of the present invention, the developing process and the rinsing process can be performed with one means. Thus, the process time can be shortened and the developing unit can be simplified.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.